Basic chromic salts and process of making same



Patented July 20, 1926.

' UNITED STATES 1,592,96i PATENT OFFICE.

HEINRICH ROSSNER AND ERNST RUNNE, OF I-IOCHST-ON-THE-MAIN, GERMANY, AS-

SIGNORS TO GRASSELLI DYESTUFF CORPORATION, OF NEW YORK, N. Y., A GOR-PORATION.

{BASIC GHROMIC SALTS AND PROCESS OF MAKING SAME.

No Drawing. Application filed December 16,1925, Serial No. 75,857, andin Germany November 8, 1924.

Solutions and suspensions of basic chromic salts-that is to say of thosesalts which contain at the most 140 parts of sulfuric anhydride (S0 to152 parts of chromic oxide (C150,) if the acid combined with thechromium is calculated as SO -when dried in the usual manner forinstance by means of a roller-apparatus yield products which can bedissolved in water only with difliculty. Apart from any additions,foreign salts etc., the solubility of the basic chromic salts is thelower with one and the same acid the more basic the salts are an thehigher the temperature is at which they are dried. For instance asolution of basic chromic sulfate Which contains 120 parts of SO to 152parts of'Cr O and has been dried in the usual manner, gives a productcontaining about 37 per cent of Gr O which is almost insoluble in coldwater and dissolves only gradually when covered over with hot water. Thesaid chromic salt can be dissolved only after having been soaked for aprolonged time in cold water and subsequently heated.

Now we have found that chromic salts of the above indicated highbasicity can be obtained in a dry state and in a form in which they arereadily soluble even in cold water and most easily soluble in hot water,by exposing the solutions or suspensions of the chromic salts in afinely subdivided, particularly in an atomized state, to a hot currentof gas or, preferably, of air. For instance a sulfate of the lastmentioned composition which has been dried in the manner just describedat 6070 O. dissolves comparatively more readily than a product which hasbeen dried by means of a roller apparatus. The said chromic .salt driedon a roller apparatus dissolves in cold water only to a very smallextent and in hot water to the extent of 1020 per cent, during the timethat the preparation dried by our new process, which is at once solublein hot water, is completely dissolved' This excellent solubility ofchromic salts of such a high basicity and containing such a highpercentage of chromic oxide as above indicated has not been knownhitherto and offers a great advantage to the tanner. 'He is notcompelled to prepare his chromium solution a long time before heproceeds to the tanning operation by soaking the product for a prolongedtime and subsequently heating as above mentioned, but he can pree parethis solution immediatelyv before he begins with the tanning operation.Further more, he can easily dissolve the basic chromic salt in thecourse of the tanning operation if, for some reason or other, he wishesto" add a further quantity of the chromic' operation are alwaysdissolved to some extent.

The solutions of the basic chromic salts may be prepared by dissolvingchromic hydroxide or basic chromic hydroxides in acids or by reducingchromates or by any other known method. Their composition may greatlyvary. There may be used salts of a single acid or of a mixtureof severalacids. There may also be employed inorganic or organic acids, such asformic acid, acetic acid or the like. The chromic salt solutions to beevaporated according to our new process may also contain othersubstances such, for instance, as a salt, sodium sulfate or the like,without impairing the result. During the drying process the temperaturemay vary within wide limits.

The following example serves to illustrate our invention:

kg. of chromic oxide, which may for instance be in the form of aprecipitate of chromic hydroxide, are dissolved by means of 60,2 kg. ofsulfuric acid of B6. and 21,8 kg. of hydrochloric acid of 20 B.,atomized in any suitable manner and dried by means of a current of hotgasses or air of, for instance, 60-7 0 C. In this manner a green powdercontaining about 36 per cent of Or o is obtained which dissolves in avery short time in cold water and immediately in hot water.

In the foregoing description and in the following claims we understandby the term solutions of a basic chromic salt to be dried also suchsolutions in which the chromic salt is only partly dissolved or issuspended therein. I

WVe claim 1. The process of preparing readily soluble basic chroinicsalts, which consists in treating solutions of chrornic salts, whichcontain not more than so much of an acid, to 152 parts by weight of Cr Oas is equivalent to 140 parts by weight of $0 in a finely subdividedcondition with a hot gas stream.

2. The process of preparing readily soluble basic chromic salts, whichconsists in treating a basic chromic salt, which contains so much ofS0,, and of C1 to 152 parts of Cr O that the total quantity isequivalent to not more than 140 parts by weight of S0 in a finelysubdivided condition with a hot as stream.

3. 'l lie process of preparing readily soluble basic chromic salts,which consists in treating solutions of .chromic salts, which containnot more than so much of an acid to 152 parts of C130 that the acid isequivalent to 140 parts of SO in a finely subdivided condition with ahot stream of a temperature of 6070 C.

1. A dry basic chroinic salt which contains not more than so much of anacid to 152 parts by weight of C150 as is equivalent to 140 parts of S0and which are readily soluble in cold water and dissolve immediately inhot water.

5. A dry basic chromic sulfate-chloride which contains not more than somuch of the acid radicals thereof to 152 parts of (112 0 as isequivalent to 140 parts of S0 which substance readily dissolves in coldwater, and innnediately in hot water.

In testimony whereof, we aitix our signatures.

HEINRICH RossNEa. ERNST RUNNE.

